1. Field of the Invention
The present invention relates to a fluid-sealed type anti-vibration rubber device such as a suspension-mount rubber and an engine-mount rubber of an automobile, which controls internal pressure by external means.
2. Description of the Prior Art
It is well known to form a liquid chamber by utilizing at least a portion of a rubber block and to divide the liquid chamber into two sections by a partitioning member, the two sections being communicated with each other by means of two separate orifices having different lengths and the orifices being used alternately.
By the way, since a valve for switching the orifices has its face closing orifice openings moving only horizontally up and down, such a problem is encountered that a turbulent flow of fluid is apt to occur in the vicinity of the orifice openings to hinder rapid switching of the orifices.
Also, since the orifices are respectively formed into a similar circular shape, a large partitioning member is indispensable to form two orifices while securing the sufficient passage length. Besides, when such two independent orifices are formed, an inlet and outlet must be provided for each orifice, requiring severe machining accuracy of the partitioning member and a high manufacturing workmanship.